Allocate HIR on an arena 1/4
This PR is the first in a series of 4, aiming at allocating the HIR on an arena, as a memory optimisation.
1. This first PR lays the groundwork and migrates some low-hanging fruits.
2. The second PR will migrate `hir::Expr`, `hir::Pat` and related.
3. The third PR will migrate `hir::Ty` and related.
4. The final PR will be dedicated to eventual cleanups.
In order to make the transition as gradual as possible, some lowering routines receive `Box`-allocated data and move it into the arena. This is a bit wasteful, but hopefully temporary.
Nonetheless, special care should be taken to avoid double arena allocations.
Work mentored by @Zoxc.
In most places, we use a span when emitting `expected...found` errors.
However, there were a couple of places where we didn't use any span,
resulting in hard-to-interpret error messages.
This commit attaches the relevant span to these notes, and additionally
switches over to using `note_expected_found` instead of manually
formatting the message
Aggregation of drive-by cosmetic changes for trait-upcasting PR
Cherry-picked from #60900.
As requested by @Centril (and @nikomatsakis, I believe).
r? @Centril
Type parameters are referenced in the error message after the previous
few commits (using span label). But when the main error message already
references the very same type parameter it becomes clumsy. Do not show
the additional label in this case as per code review comment by
@estebank.
Also this contains a small style fix.
Fixes#47319.
Shows the type parameter definition(s) on type mismatch errors so the
context is clearer. Pretty much changes the following:
```
LL | bar1(t);
| ^
| |
| expected enum `std::option::Option`, found type parameter `T`
```
into:
```
LL | fn foo1<T>(t: T) {
| - this type parameter
LL | bar1(t);
| ^
| |
| expected enum `std::option::Option`, found type parameter `T`
```
Remove `InternedString`
This PR removes `InternedString` by converting all occurrences to `Symbol`. There are a handful of places that need to use the symbol chars instead of the symbol index, e.g. for stable sorting; local conversions `LocalInternedString` is used in those places.
r? @eddyb
It's a full conversion, except in `DefKey::compute_stable_hash()` where
a `Symbol` now is converted to an `InternedString` before being hashed.
This was necessary to avoid test failures.
